The current methods of delivering video data over existing television, telephone and computer networks require either fixed transmission methods or possible lower transmission quality.
The transmission of images and full motion video data over television networks has evolved from (i) broadcast television transmitting fixed schedules of programming, (ii) to multiple channel cable television, available to local CATV subscribers, (iii) to pay-per-view programming, where subscribers place an order with the cable operator for the subscriber's descrambling of a scheduled program to permit subscriber viewing at a designated time.
Due to the emergence of more sophisticated, standardized digital compression techniques like Motion Pictures Experts Group (MPEG), and switched, scalable protocols like Asynchronous Transport Mode (ATM), more video data in a compressed, switchable form can be transmitted along virtual channels through the existing telephone line, cable or satellite transponder communications infrastructure. Video signals typically take up about 140 Mb/s of bandwidth. Initial source encoding and compression can reduce this to 45 Mb/s. MPEG compression techniques can now reduce these signals to 1.5 Mb/s for VCR video to 12 Mb/s for realtime, sports network quality. Most CATV systems deliver 450 MHz or 550 MHz to the household at 6 MHz per television channel, with rebuilds delivering 750 MHz. The upper 5-45 MHz can be used for emerging digital delivery, where a 1.2 Mb/s video signal compression can transform a single 6 MHz channel into supporting 12-14 VCR quality channels. The penetration rate of these reception capabilities, however, will take several years to implement, and until that time, other intermediate, interactive video reception strategies like the following patent examples, have been proposed.
Literal et al. U.S. Pat. No. 5,247,347 describes a PSTN architecture for video-on-demand systems, as well as subscriber control of video programming delivery. Accordingly, subscribers are provided with an interface unit including a local loop node for receiving a multiplexed signal from a subscriber local loop. The Central Office interface to the subscriber can receive video signals from a video information provider, and telephone voice and data from the subscriber, the latter allow the subscriber to digitally interact with a Video Information Provider (VIP) system, to enable it to receive buffered digital video signals from a remote Central Office video database through a Digital Cross-Connect (DCS) provided by the PSTN. This digital interaction provides for the selection of a wide variety of selected compressed video/audio data programs, including feature films, music videos, medical and commercial imaging, video phone, video conferencing and video games. Various combinations of voice and data interaction of the subscriber with the VIP are possible, but in all cases video control data is provided over the subscriber loop, which may be coaxial cable, optical fibre or telephone lines from the subscriber's premises to the video buffer in the VIP system, which controls the receipt of video signals.
The subscriber's local loop for the receipt of the compressed video signal must support a 1.5 MB/s digital transmission, or be comprised of a D1 channel (normally a 24 telephone line bundle) overlaid with the standard telephone service signaling.
An alternative to centralized television or cable video distribution systems are video telephony systems, where multiple system users generate their own video transmissions. These PSTN systems are often bandwidth limited, providing only still frame or limited motion video conferencing capabilities, though recently, digital telephone access lines, such as ISDN, can provide scalable better quality. Digital access facilities to consumer homes, however, are not readily available because they require expensive bandwidth commitments through multiple lines or fibre optic links to the nearest telephone company ISDN switch.
In Papanicolaou et al. U.S. Pat. No. 5,278,889, a video telephony system is proposed using cable-television-telephony and a special method of video telephony dialing to overcome some issues of household video telephone cost. Digital bandwidth access limitations for full motion video to the household are viewed as a significant limitation, and these will not be overcome until all homes are provided with fibre access. Hence, a system involving a coaxial cable network, preferably part of an existing cable television system, is proposed to provide a local access link for the transmission of video telephone signals between each originating and destination location and a respective "head end" located on the cable company premises. Each of the head ends is connected to a Point of Presence (POP) of a telephone common carrier, such as AT&T, so that a connection between pairs of head ends, and thus between a pair of video telephone locations, can be made via a switched network maintained by the carrier.
Hence, the cable subscriber can "borrow" part of the RF cable bandwidth not used for entertainment channels and use it for video telephony. A demodulated audio and video signal from a consumer-type camera or camcorder at the subscriber's home is converted to a compressed digital signal, multiplexed with other digital signals on the trunk line and sent to carrier's local POP as a 384 Kb/s composite signal using an ISDN Primary Rate Interface (PRI) connection. Thus, a video telephone number, which could be the same as the subscriber's standard 10-digit telephone number that uses a video capable extension, provides the subscriber with a video telephony dial-up connection through the network.
In the Papanicolaou et al. system, calls are always initiated and completed by the subscriber, with a Network Control Point (NCP) database containing coaxial cable connection path information along with the ISDN bandwidth subscription of the subscriber to provide an automatic telephone call link to a subscriber with similar carrier/cable head end or straight ISDN connectivity to another local exchange. Transmission rate information in the NCP database is also used for rate revision as a video call is being made, if it is discovered that destination subscriber's equipment can only support a lower rate. Hence, the caller's local POP is instructed by the system to re-initiate the call at the lower rate.
As mentioned before, bandwidth capabilities and the network infrastructure required to support the bandwidth necessary for digital video communication can define the quality of the video image. The 384 Kb/s composite signal rate described in the Papanicolaou et al. system is not television quality and not video quality, which at present, given the best MPEG2 compression capabilities, still requires at least 1.5 Mb/s of bandwidth.
In Baji et al. U.S. Pat. No. 5,027,400, a bidirectional, interactive multimedia system is discussed as a combination of cable and a broadband ATM network, the purpose of which is to deliver television commercials requested by subscribers over a cable television network. The desired program and advertisement are delivered to the subscriber via an ATM exchange, and a subscriber video buffering and mixing system encodes the retrieved video or still image information into the cable television channel feed of the subscriber's choice. The system is essentially an on-demand video/image clip database management system, using cable channels for direct to household transmission.
Existing video-on-demand systems are notionally an approximation of a per transmission based delivery system, but their transmission capabilities are defined by the notion of one sender and multiple subscribers retrieving video information from a central office video database. The network controls do not require the degree of traffic scheduling and bandwidth control per transmission that would be necessary for varying numbers of senders and receivers at varying locations, sending varying durations of video data.
Normally, corporate clients lease permanent transmission bandwidth from a PSTN or private network, which is defined by leased bandwidth access. The scale of this access is defined by total corporate needs and is not expressed on a per transmission basis. It requires either a dedicated broadband, point-to-point channel to each destination, or a broadband access line connection to the nearest PSTN POP that handles Switched Multimegabit Digital Services (SMDS). Needless to say, the leasing charge for such dedicated channels or broadband access is beyond what any individual consumer could afford. However, the maintenance of this access allows corporate clients to transmit bulk data at their discretion.
A consumer-scoped video messaging system today could assume the form of a video telephony system as discussed in the prior art. However, the continual maintenance traffic and bandwidth capabilities related to the requirements of on-demand, bidirectional user control, presupposes constant parameters that imply bandwidth and broadcast restrictions. Bandwidth is a subscription bandwidth, and uniform throughout the network at set subscriber rates. The subscriber cannot invoke bandwidth that is greater for some transmissions and less for others. This would present an unmanageable traffic problem. Broadcast routing, in the form of conferencing call bridging, must be limited to a few participants. This is due to the node architecture and bandwidth uniformity for all transmissions along the transmission paths of the video telephony network.
Discussions of video mail systems in conference literature on computer networks refer to as a feature of the message-based, common channel signaling protocol of multimedia desktop computer workstations. Networked parties can communicate in several ways using network-informing, call messaging type formats, video mail being one of several realtime messaging types. Video mail is also understood as a special video clip message subset of electronic mail or e-mail. It is described as possessing a new protocol structure, like MIT's Multipurpose Internet Mail Extensions (MIME) protocol, which allows computer workstation users to address and transmit video clips as a supplement to the Internet standard Simple Mail Transfer Protocol (SMTP) for e-mail.
Multimedia "mailboxes" are similar to e-mail mailboxes. They allow computer workstation users to transmit and retain video mail messages to each other, by providing a multimedia computer directory structure. They can also be used to send video mail messages from a user to a process or a process to a process, to produce a combined end result, like an animated computer graphic composite on realtime video. However, computer networks are essentially fixed transmission systems, involving fixed topologies, predetermined messaging controls and uniform bandwidth, based on a required upper limit traffic handling capability.
The object of the invention is to solve one or more of the drawbacks in existing systems discussed above, or to provide other improvements to the art.